1. Field of the Invention
The invention relates to an optical connector for connecting optical fibers to each other, and also to a method of attaching the optical connector.
2. Description of the Related Art
Conventionally, a connecting method is employed in which a short optical fiber is previously attached to a ferrule of an optical connector and an optical fiber to which the optical connector is to be connected is then connected to the short optical fiber. In the method, since the short optical fiber is previously attached to the ferrule, the front end of the ferrule can be previously polished under a state where an optical fiber is attached. Therefore, it is not required to conduct a polishing work during a work of attaching the optical connector to an optical fiber, thereby producing an advantage that the work of attaching the optical connector can be completed in a short time.
In each of optical connectors disclosed in Japanese patent publication (Kokai) No. SHO 63-186205, Japanese patent publication (Kokoku) No. HEI 7-69498, and Japanese patent publication (Kokai) No. SHO 64-72105, a short optical fiber of a ferrule is connected to an optical fiber to which the connector is to be attached, by means of fusion or adhesion. The connection due to fusion has a problem in that a fusing apparatus is required, and that due to adhesion has a problem in that a prolonged time period is necessary for conducting the adhesion work. In the case where an ultraviolet-setting resin is used in adhesion, there is another problem in that an ultraviolet irradiator is necessary. When a fusing apparatus or an ultraviolet irradiator is used, there arises a further problem in that a place for installing such an apparatus and a power source must be ensured. Consequently, such methods are not always suitable for a work in the field.
Japanese patent publication (Kokai) No. SHO 63-8613 discloses an optical connector having a cylindrical ferrule consisting of two capillaries. The optical connector is assembled while a short optical fiber is previously fixed to one of the capillaries, and the fixed optical fiber is inserted to the other small bore. The optical fibers are contacted with each other in the small bore. Also an optical connector disclosed in Japanese patent publication (Kokai) No. HEI 6-337325 employs a method in which an optical fiber to which the optical connector is to be connected is contacted with a short optical fiber in a small bore of a capillary. In the case where a capillary is used as described above, since two optical fibers are not fixed in the coupling portion, there is a problem in that variation of the ambient temperature or an operation of handling the optical connector may easily cause misalignment and a gap between the cores of the optical fibers, which are main factors of variation of the optical loss.
By contrast, an optical connector proposed in Japanese patent application No. HEI 7-283420 has a configuration in which a semispherical space is formed at a center portion of a ferrule ,a short optical fiber and an optical fiber to which the optical connector is to be attached are butted together on the ferrule and in the space, and a holding member is fixed to the space, thereby pressing the optical fibers. In the optical connector, fusion and adhesion are not conducted, and hence a fusing apparatus is not necessary and a time period of conducting an adhesion work is not required. Therefore, the proposed optical connector has an advantage that the work of connecting optical fibers together can be completed in a short time. Since the coupling portion of the two optical fibers is pressed by the holding member, moreover, there is an advantage that the coupling state can be ensured. However, the optical connector has the following problem. since a ferrule of a special structure is used, a groove in which optical fibers are butted together is a half-round groove having a shape which is formed b splitting an optical fiber hole into halves. Consequently, the axial misalignment is larger in degree as compared with the case where a V-groove is used.